One of the main disadvantages of intact canal wall mastoid surgery for cholesteatoma is the necessity of the "second look". The morbidity of a second procedure can be reduced, however, with the aid of a rigid endoscope. Fifty-five consecutive patients undergoing a re-exploration were included in this study. Prior to surgery computerized tomography (CT) was performed in order to assess both the anatomy and degree of pneumatisation of the middle ear cavity and mastoid bowl. The operative findings at the time of the "second look" were correlated with the pre-operative scans. An otoendoscopic approach was possible in all cases. In the diagnosis of residual or recurrent disease, the CT scan had a sensitivity of 43.8%. The specificity of the CT scan was 51.3%. The explanation for these findings is that it is impossible to differentiate between recurrence, scar tissue or inflammation on CT images in patients who have undergone previous mastoid surgery.